Publishers are now beginning to provide content for viewing on-line using web browsers and other network enabled applications. Some of the published content includes display pages having a fixed-layout or fixed presentation format. Conventional formats having or defining a fixed-layout or fixed presentation for document contents are useful for maintaining a layout designed by an author or publisher. Fixed-layout document layouts appear approximately the same to each of multiple viewers regardless of what processor, hardware, operating system, or printer generates the document. In other words, once content is rendered in a particular configuration, the content does not adapt to changes in a viewport size.
Fixed-layout documents have a history that originates from the print world. Such documents essentially describe exactly where ink goes on a display page. For example, such fixed-layout formats instruct a printer or display screen exactly where on the display page to draw the letter “C,” or where to draw the letter “H,” or where to draw a line, or where to draw a curve. Such letters are defined in the fixed layout to be in a certain location relative to each other regardless of a size of the printed content.
A common and popular example of a fixed-layout file format is the Portable Document Format (PDF). PDF is a file format created by Adobe Systems Incorporated of San Jose, Calif., U.S.A. PDF is an open standard that was officially published on Jul. 1, 2008 by the International Organization for Standardization (ISO) as ISO 32000-1:2008.
Computer systems are capable of presenting information or content to people in a variety of ways. As an example, modern computer systems can present content to users such as playing movies or other multimedia presentations, displaying web pages, slide shows, text presentations, animations, audio or music, video games and the like. Prior to being displayed, a content developer, publisher or author creates the content using one or more software application programs that provide an authoring environment designed specifically for purposes of content creation. As an example, word processors allow an author to create text content, web page development applications provide an authoring environment to allow an author to create web pages, and multimedia authoring applications allow content authors to create video, animations, and other types of interactive content. Generally then, authoring environments are software programs that operate on computer systems and allow people (i.e., authors and publishers) to create, transform, or author creative content. Computerized authoring environments provide authoring features, elements, or toolkits within a user interface for viewing and creating content and storing such content. For example, some authoring environments provide toolkits to enable people to create content such as software application, simulations, websites, movies, audio or music or multimedia content.
In some graphical applications a viewport is the visible portion of a two dimensional (2D) area in a fixed layout document or page that may be larger or smaller than the visualization device. The viewport is navigated, scrolled and/or paged via a pointing device, such as a mouse, touchpad or trackball, to select, activate, and provide input to the application. Accordingly, a user can navigate and view different content regions via movement of a pointing device or keyboard.
A viewport can be zoomed to display content regions at various sizes. Increasingly, mobile devices such as PDAs, laptops, and cellular telephones are being used for presenting content to users. Such content is anything that can be viewed on a display screen. For example, such content includes published magazines which are now made available for viewing on mobile devices. Users typically scroll through a display page horizontally and vertically across the screen to reveal successive content.
Certain conventional software applications operate within a computer system to allow users to manipulate a scroll bar, a keypad or a touch sensitive screen to view and browse content. For example, in a word processing application, a document may consist of multiple pages, yet the word processing application's current settings provide a view of a single page at a time. In order to view other pages, a user can manipulate a scroll bar, press directional keys or swipe a finger across a touch sensitive screen to view pages that occur after the currently visible page or before the currently visible page. In another example, a current view of a browser application may not be big enough to create a complete view of an entire web page. In order to view all the web content presented on the web page, the user can manipulate the browser application's scroll bar upwards and downwards or left and right to view various portions of the web page. Users can also change the text size by manually adjusting a zoom level.